This invention relates in general to radial piston pumps of the so-called top loading type.
A top loading type of radial piston pump is disclosed, for example, in German Patent No. OS 22 42 435. In pumps of the foregoing type, an inflow of fluid is received within a fluid displacing piston at its radially outer end remote from the drive cam with which the piston is engaged for reciprocation. Inflow of fluid is conducted to the piston through an intake passage which is closed off during the fluid displacing stroke of the piston. The fluid displaced by the piston is conducted to an outlet pressure line through a check valve from which the fluid is then conducted to a fluid operated device. During the fluid displacing stroke, the radially outer end portion of the piston moves across a relatively short sealing surface portion of the piston bore within which the piston is reciprocated, such sealing surface portion being located radially outward of the inlet passage. A slight overlap between the inlet passage and the piston is often the cause of fluid leakage loss during the fluid displacing stroke of the piston.
It is therefore an important object of the present invention to minimize fluid leakage past the fluid displacing piston at the shortest sealing surface portion between the inlet passage and the pressure chamber into which the fluid is displaced in a radial piston pump of the top loading type.